Carrier-concentration dependent photoluminescence of InAsN films grown by RF-MBE

The observation of bandgap reduction in InAsN by optical absorption is often somewhat obscure due to the band-filling effect caused by the high electron concentration associated with N incorporation. In this report, the detailed photoluminescence properties of 1.6-μm-thick InAsN films grown on semi-insulating GaAs(0 0 1) substrates by RF-MBE are investigated in relation with the carrier concentration. The PL peak energy at 10 K clearly exhibits a redshift with increase in N content up to 1.84%, whereas it tends rapidly to a blueshift for N contents above 2.39%. The redshift is consistent with the bandgap reduction caused by the N incorporation, whereas the blueshift is attributed to the band-filling effect caused by the highly concentrated degenerate electrons. Moreover, it is found that the temperature dependent PL and the excitation power dependent PL are largely affected by carrier concentration and the potential fluctuations due to the non-uniform incorporation of N into the host. The bowing parameter c estimated from fitting with the quadratic curve, (1−x)EG,InAs+xEG,InN-c(1−x)x, is 2.2 eV.